Hierarchical Stateful Path Computation Element (PCE)
RFC 8751

Document Type RFC - Informational (March 2020; No errata)
Authors Dhruv Dhody  , Young Lee  , Daniele Ceccarelli  , Jongyoon Shin  , Daniel King 
Last updated 2020-03-31
Replaces draft-dhodylee-pce-stateful-hpce
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IESG IESG state RFC 8751 (Informational)
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Internet Engineering Task Force (IETF)                          D. Dhody
Request for Comments: 8751                           Huawei Technologies
Category: Informational                                           Y. Lee
ISSN: 2070-1721                                      Samsung Electronics
                                                           D. Ceccarelli
                                                                Ericsson
                                                                 J. Shin
                                                              SK Telecom
                                                                 D. King
                                                    Lancaster University
                                                              March 2020

          Hierarchical Stateful Path Computation Element (PCE)

Abstract

   A stateful Path Computation Element (PCE) maintains information on
   the current network state received from the Path Computation Clients
   (PCCs), including computed Label Switched Paths (LSPs), reserved
   resources within the network, and pending path computation requests.
   This information may then be considered when computing the path for a
   new traffic-engineered LSP or for any associated/dependent LSPs.  The
   path-computation response from a PCE helps the PCC to gracefully
   establish the computed LSP.

   The Hierarchical Path Computation Element (H-PCE) architecture allows
   the optimum sequence of interconnected domains to be selected and
   network policy to be applied if applicable, via the use of a
   hierarchical relationship between PCEs.

   Combining the capabilities of stateful PCE and the hierarchical PCE
   would be advantageous.  This document describes general
   considerations and use cases for the deployment of stateful, but not
   stateless, PCEs using the hierarchical PCE architecture.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are candidates for any level of Internet
   Standard; see Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8751.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction
     1.1.  Background
     1.2.  Use Cases and Applicability of Hierarchical Stateful PCE
       1.2.1.  Applicability to ACTN
       1.2.2.  End-to-End Contiguous LSP
       1.2.3.  Applicability of a Stateful P-PCE
   2.  Terminology
     2.1.  Requirements Language
   3.  Hierarchical Stateful PCE
     3.1.  Passive Operations
     3.2.  Active Operations
     3.3.  PCE Initiation of LSPs
       3.3.1.  Per-Domain Stitched LSP
   4.  Security Considerations
   5.  Manageability Considerations
     5.1.  Control of Function and Policy
     5.2.  Information and Data Models
     5.3.  Liveness Detection and Monitoring
     5.4.  Verification of Correct Operations
     5.5.  Requirements on Other Protocols
     5.6.  Impact on Network Operations
     5.7.  Error Handling between PCEs
   6.  Other Considerations
     6.1.  Applicability to Interlayer Traffic Engineering
     6.2.  Scalability Considerations
     6.3.  Confidentiality
   7.  IANA Considerations
   8.  References
     8.1.  Normative References
     8.2.  Informative References
   Acknowledgments
   Contributors
   Authors' Addresses

1.  Introduction

1.1.  Background

   The Path Computation Element communication Protocol (PCEP) [RFC5440]
   provides mechanisms for Path Computation Elements (PCEs) to perform
   path computations in response to the requests of Path Computation
   Clients (PCCs).

   A stateful PCE is capable of considering, for the purposes of path
   computation, not only the network state in terms of links and nodes
   (referred to as the Traffic Engineering Database or TED) but also the
   status of active services (previously computed paths, and currently
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